Smithsonian at the Poles: Contributions to International Polar

off Uruguay (34º43�S, 49º28�W to 34º51�S, 49º44�W) in
the southwestern Atlantic north of the Subtropical Convergence
(Park, 1978).
Paraeuchaeta parvula, like P. biloba, has also been
collected both north and south of the Antarctic Convergence.
Paraeuchaeta dactylifera has only been found in
relatively small numbers and usually in the subantarctic
region; two specimens captured well south of the Antarctic
Convergence (Park, 1978) are exceptions. Two aetideid
species, Aetideus australis and Pseudochirella mawsoni,
can also be found both north and south of the Antarctic
Convergence. Aetideus australis has been collected more
often in waters north of the convergence than south. Pseudochirella
mawsoni has been reported from numerous localities
in the Southern Ocean and has been collected in
large numbers in midwater trawls immediately north of
convergence. Both species are presumed to be carnivores.
Four very common scolecitrichid species are endemic
to the Southern Ocean. Scolecithricella dentipes and
Scaphocalanus farrani are found throughout the Antarctic
and subantarctic regions, where they may be numerous
in some samples. Scaphocalanus parantarcticus and Scolecithricella
schizosoma are also distributed throughout the
Southern Ocean and may be very common but are found
in smaller numbers than the fi rst two.
There are four species of the family Heterorhabdidae
that are well-known endemics of the Southern Ocean: Heterorhabdus
pustulifer, H. austrinus, Heterostylites nigrotinctus,
and Paraheterorhabdus farrani. Paraheterorhabdus
farrani is common and has been collected throughout the
Southern Ocean; Heterorhabdus pustulifer and H. austrinus
are also common, while Heterostylites nigrotinctus is
rare. Among the remaining 4 of the 19 endemic species reported
from both Antarctic and subantarctic regions, three
rare species, Candacia maxima, Cephalophanes frigidus,
and Metridia pseudoasymmetrica, and the common Pleuromamma
antarctica are not often encountered in samples.
However, there are enough records to suggest that these
species are limited to the Southern Ocean.
There are seven deepwater species that have been
found only in the subantarctic region (Table 3). Six of
them, Aetideopsis tumerosa, Bathycalanus eltaninae,
B. unicornis, Bradycalanus enormis, B. infl atus, and B.
pseudotypicus, are known from a few localities and only
a few specimens; their distribution cannot be determined
with certainty. Of these six species, the latter fi ve belong
to the family Megacalanidae; Aetideopsis tumerosa is an
aetideid. The seventh species, Candacia cheirura, has been
collected often enough to be considered the only species
of Candaciidae restricted to the subantarctic region. It is
PELAGIC CALANOID COPEPODS OF THE SOUTHERN OCEAN 153
common and has been hypothesized to be restricted to mesopelagic
waters of the West Wind Drift (Vervoort, 1957),
also called the Antarctic Circumpolar Current, which is
the dominant circulation feature of the Southern Ocean.
In summary, among the 50 deepwater calanoid copepod
species found exclusively in the Southern Ocean, six
species occur close to the continent. Although these species
have been captured in relatively small numbers, they may
have been undersampled due to the diffi culty in collecting
with a midwater trawl in deepwater close to the continent.
Among these six species, the closely related Paraeuchaeta
austrina, P. erebi, and P. tycodesma, all members of the
antarctica species group, appear to be restricted to the
same habitat. Of the 18 species found in open waters
south of the Antarctic Convergence, four were originally
described from one or two specimens collected in a single
sample, have not been rediscovered, and remain poorly
known. The remaining 14 species can be regarded as typical
endemics of the Antarctic deep water. Except for two
relatively rare species, they are common or very common
in waters south of the Antarctic Convergence. Nineteen
of the 50 Southern Ocean deepwater species are typical
endemics of the region as a whole, and most of them have
been collected from many localities throughout the Southern
Ocean. Seven of these species have only been found in
the subantarctic region. Their distributions are based on a
small number of specimens and therefore are insuffi ciently
known. Candacia cheirura is an exception; it is a common
endemic of the subantarctic region.
DEEPWATER CALANOIDS FROM ANTARCTIC
WATERS REPORTED NORTH OF THE
SUBTROPICAL CONVERGENCE
A total of 127 deepwater species of pelagic calanoid
copepods have been reported from the Southern
Ocean south of the Antarctic Convergence. Twenty-four
of those species are limited to this region (see the Deepwater
Calanoids Restricted to the Southern Ocean section),
and 19 species have been found northward, into
the subantarctic region, with their distribution terminating
at the Subtropical Convergence. Thus, 43 of these
127 deep water species collected south of the Antarctic
Convergence are endemic to the Southern Ocean.
The remaining 84 species have been reported beyond
the Subtropical Convergence to varying degrees. Seven
(8%) of these species have been collected in the south temperate
region, adjacent to the Southern Ocean (Table 4),
and fi ve (6%) species have been collected as far north as